There's inevitability in the way it crumbles (6)
I believe the answer is:
cookie
'it crumbles' is the definition.
The definition suggests a singular noun which matches the answer.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for cookie that I've seen before include "Computing identifier; biscuit (American)" , "that sits on computer" , "Piece of computer data" , "US bicky" , "Identifying data; biscuit" .)